Method and machine for cutting threads of varying pitch



0 L. F. DURAN Aug 1964 METHOD AND MACHINE FOR CUTTING THREADS 0F VARYINGPITCH 5 Sheets-Sheet 1 Filed June 15 1962 INVENTOR.

4O D RA/V Aug. 25, 1964 L. F. DORAN 3,145,599

METHOD AND MACHINE FOR CUTTING THREADS 0F VARYING PITCH 3 Sheets-Sheet 2Filed June 15, 1962 INVENTOR. I

450 f. DORA/V ATTORNEYS L. F. DORAN 1964 METHOD AND MACHINE FOR CUTTING3145599 THREADS 0F VARYING PITCH 3 Sheets-Sheet 3 Filed June 15, 1962INVENTOR ATTOR/VEXJ United States Patent 3,145,599 METHQD AND MACHINEFOR CUTTING THREADS OF VARYENG PITCH Leo F. Duran, Clawson, Mich,assignor to Beaver Preeision Products, line, Ciawson, Mich, acorporation of Michigan Filed .lune 15, 1962, Ser. No. 292,736 (Ii-aims.(Cl. 82-14) This invention relates to a method and machine for cuttingthreads or threadlike forms or grooves of varying lead or pitch.

Screws or other like shafts having a spiral configuration thereon arefrequently used in manufacturing operations for the purposes ofconveying or timing members connected therewith and are also used suchas in the molding of plastic materials for the purpose of transferringor compacting material. With such screws or spirally configured shafts,it is often desirable to be able to cause some portions or all of thelead or pitch of the spiral thread or groove to accelerate or deceleratein order to obtain a speeding up or a slowing down of the member ormaterial moved.

With specific reference to extrusion type screws used in plasticmolding, it is also desirable in many instances to reduce the crosssectional area of the groove in a longitudinal advancing direction forthe purpose of progressively increasing the compressing or compacting ofthe plastic material being conveyed by the screw. Thus, in theoperations described, it is essential to have a screw or other spirallyconfigured shaft wherein the lead or pitch of the spiral thread orgroove deviates from a constant value at least along certain portions ofthe screw or shaft and in some instances, in addition to theacceleration or decleration of the thread or groove lead, it is alsonecessary to vary the depth of the thread or groove root.

It is an object of this invention to provide a method and apparatus formachining spiral threads or grooves in a manner such that the lead orpitch thereof can be varied in accordance with a predeterminedrequirement.

A further object of the invention resides in a method and apparatus formachining spiral threads or grooves in a manner such that both the leador pitch of the thread or groove as well as the root depth thereof canbe simultaneously varied in accordance with a predetermined requirement.

A further object of the invention is to provide a method and apparatusof the type described wherein the lead or pitch of the thread or grooveis varied in accordance with the operation of a pattern controlledtracer.

A further object of the invention is the provision of a method andapparatus of the type described wherein the lead or pitch of the threador groove is variably controlled by one tracer and the depth of thethread or come apparent from the following description and drawings inwhich:

FIG. 1 is a fragmentary front elevational view of a machine toolincorporating the method and apparatus of the present invention.

FIG. 2 is a fragmentary side elevational view partly in section of themachine tool shown in FIG. 1.

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FIG. 3 is a fragmentary top elevational view of the machine tool shownin FIG. 1.

FIG. 4 is a schematic view illustrating the type of thread or groovethat is adapted to be machined by means of the method and apparatus ofthe present invention.

Referring to FIG. 1, there is shown by way of illustration a latheincorporating the apparatus of the present invention. The machine toolwith which the invention is usable is by no means limited to a lathe,the invention being applicable to other types of machine tools as well.The lathe illustrated includes a power-driven chuck 10 and a tail stock12 between which the shaft 14 on which a thread or spiral groove to bemachined is supported for rotation. As is conventional, the latheincludes a bed 16 provided with ways 18 for guiding the carriage 20lengthwise of the shaft 14. Carriage 20 is arranged to be driven at auniform rate axially of shaft 14 by means of a power-driven lead screw22. A cross slide 24 is supported on carriage 20 and is guided formovement transversely of the axis of shaft 14 by ways 26. The adjustmentof cross slide 24 transversely of shaft 14 is eifected in a conventionalmanner by a hand wheel 28 which drives a screw, not illustrated, thatinterconnects the cross slide and carriage. Cross slide 24 is in turnprovided on its upper face with ways 30 in which are mounted a toolblock assembly 32 and a dual tracer mounting assembly 34 (FIG. 2).

Tool block assembly 32 includes a base plate 36 provided with ways 38 inwhich a tool block slide 40 is mounted for movement in a directionparallel to the ways 18 of the lathe bed. At one end of base plate 36,there is fixedly mounted a hydraulic cylinder 42 (FIG. 1) enclosing apiston, not illustrated, having a piston rod 44 connected with slide 40such that when cylinder 42 is actuated, slide 40 is shiftedlongitudinally on base plate 36. A tool block 46 is mounted on slide 40and is provided with means for rigidly supporting a cutting tool 48.I-Iandwheels 50 and 52 enable adjustment of the cutting tool 48lengthwise and transversely of slide 40, that is, in a direction axiallyand radially, respectively, of the shaft 14 supported between the headstock 10 and the tail stock 12 of the lathe.

The tracer mounting assembly 34 includes a base plate 54 mounted on thetransversely extending ways 30 of cross slide 24. Base plate 54 isprovided with ways 56 parallel to the ways 38 on the base plate 36 onthe tool block assembly 32. A column member 58. is mounted in the ways56 of base plate 54 and is interconnected by a rigid brace 60 with thetool block slide 40. A bydraulic cylinder 62 mounted on cross slide 24has its piston rod 64 interconnected with the base plate 36.

Thus, the column member 58 is constrained to move axially andtransversely of the axis of the work piece 14 with tool block slide 40.

A hydraulic tracer 66 of conventional design is mounted on column 58 sothat its stylus or finger 68 projects upwardly'and is adapted to followthe tracing edge 70 of a horizontally disposed template '72. Tracer 66isoperably associated with cylinder 62. so that in following the edge 70of template 72, tracer 66 controls the movement of the tool 48 in adirection transversely of the axis of work piece 14 and thus determinesthe depth of the groove being out along the axis of the work piece.Column 58 is provided with vertical Ways 74 in which is slidably,

is operably associated with cylinder 42 so that in follow-' ing the edge84 of template 86, it controls the movement of tool 48 axially of thework piece on cross slide 24. Thus, the contour of the tracing edge 84determines the advance of the tool 48 relative to cross slide 24 andthus determines the lead on the thread or spiral groove being cut.

In order to enable the tracer 80 to follow the tracing edge 84 oftemplate 86, cam plate 78 is fashioned with a diagonally extending camedge 88 which is disposed at an angle of 45 to the plane of horizontalmovement. Base plate 54 at one end is formed with a vertically extendingcolumn Sltl provided with vertically extending ways 92 in which avertical slide 94 is arranged for sliding movement. Slide 94 supports aroller 96 which serves as a cam follower for the cam plate 78.Thevertical position of slide 94 is adapted to be adjusted by turning ahandwheel 98 which, through a pair of bevel gears 19%), 192, rotates ashaft 104 which threads into the lower end of slide 94. Thus, ashandwheel 98 is rotated, slide 94 and the cam follower roller 96 arecaused to shift vertically. It will be appreciated that with thisarrangement, when the column member 58 shifts axially of the work pieceon the base plate 54 while the cam edge 88 of cam plate 73 is inengagement with cam roller 96, tracer 8G is shifted vertically. In theparticular arrangement illustrated, the degree of vertical shifting oftracer 80 is exactly equal to the extent to which it is shiftedhorizontally on base plate 54.

In the above described arrangement, the horizontally disposed template72 has its tracing edge 70 contoured so as to produce the desiredvariation in the depth of the thread or groove being machined andlikewise, the tracing edge 84 of the vertically disposed template 86 iscontoured so as to produce the desired lead in the thread beingmachined. It will be appreciated that suitable switches and mechanismnot illustrated are provided for energizing lead screw 22 and thecircuits of tracers 66 and 88. In the full retracted position of thetool block assembly 32, that is, with piston rod 44 fully extended andpiston rod 64 fully retracted, the fingers 68 and 82 of both tracers areretracted to positions out of engagement with their respectivetemplates. In the fully retracted position of the tool block assembly,the triangular cam plate 7% assumes the position indicated by brokenlines 106 in FIG. 1 where the cam edge 8% is out of contact with the camfollower roller 96.

To initiate the thread cutting operation, start switches, notillustrated, are actuated to energize tracers 66 and 80. When tracer 66is energized, cylinder 62 is actuated to shift the tool block assembly32 and the tracer mounting assembly 34 inwardly until the stylus 68contacts the tracing edge '70 of template '72. As is conventional, theengagement of the stylus as with the tracing edge 72 arrests thetransverse inward movement of the tool. When tracer 39 is energized,piston rod 44 is retracted to shift the tool block 46 and the column 58on which the two tracers are mounted in a direction toward the right asviewed in FIGS. 1 and 2 on the cross slide 24. As soon as the cam edge33 of the triangular cam plate 78 engages cam roller 96, tracer 843 isshifted upwardly and its upward movement as well as its axial movementis arrested when its stylus 32 contacts the tracing edge 34 of template86. The initial depth of cut and the axial positioning of the tool bititself may be adjusted by turning handwheels 52 and 50, respectively.The point at which the thread to be machined is picked up on the workpiece is adjusted by manipulating handwheel 93 so as to raise or lowertracer iii? and thereby shift the tool block axially on the cross slide.

After these adjustments have been made, the switch for energizing thelead screw 22 is actuated and the tool bit 48 will thereafter follow apath determined by the contours of the tracing edges 76 and 84 of theirrespective templates 72 and 86. It will be appreciated that the speed ofrotation of chuck it is related to the speed of rotation and the lead ofscrew 22 as is conventional in a thread cutting lathe so as to determinethe initial pitch of the thread to be cut. As the stylus 6% follows thetracing edge '79, the tool 48 will move progressively into the workpiece 14 as it travels lengthwise thereof to progressively increase thedepth of the thread or groove being machined. In the same manner as thestylus 32 of tracer follows the tracing edge 34 of template 86, the toolwill be shifted progressively to the right on the cross slide 24 asviewed in FIG. 1 and thus, the lead of the thread or spiral groove beingcut will be progressively increased over that which would be otherwiseproduced by the lead screw 22 alone. In this connection, it will benoted that the cam plate '78 maintains the stylus 82 of tracer 80 incontact with the tracing edge 84 of template 36. By arranging the tracer80 so that it is shifted vertically, it will be appreciated that thenecessary deflection required of the finger or stylus 82 is very smalland consequently, the amount of oil controlled by the tracer valve isrelatively small.

In the embodiment illustrated herein, the contours of the tracing edgesof the two templates 72 and 86 are designed to produce a progressivelyincreasing depth of groove and a progressively increasing lead. Theprogressively increasing lead is illustrated schematically in FIG. 4 asby L and L and the increasing depth of the thread is illustrated as Dand D It will be appreciated that the tracing edges of these templatescan be designed to produce any variation in depth of groove or leaddesired. It will also be appreciated that the templates can also bedesigned to produce a decreasing pitch and depth of groove.

In the claims, the term thread is used in a broad sense to designate anyhelical or spiral groove.

I claim:

1. In a machine or cutting a thread, the lead of which varies along theaxis of the thread, the "combination comprising a base, means on thebase for supporting a workpiece to be threaded and for rotating theworkpiece about a horizontal axis, a carriage on said base, means formoving the carriage horizontally on the base in a direction axially ofthe rotating workpiece and at a uniform rate in timed relation to thespeed of rotation of the workpiece so that the carriage moves lengthwiseof the thread to be cut at a rate corresponding to the initial lead ofthe thread to be cut, a cross slide on said carriage and movablehorizontally thereon in a direction normal to the direction of travel ofthe carriage, .a support member mounted on the cross slide for movementhorizontally in a direction parallel to the path of movement of thecarriage, a cutting tool on said support member, a hydraulic cylinderinterconnecting the cross slide and said support member for moving thesupport member on said cross slide in said direction parallel to thepath of movement of the carriage, a template on said base having atracing edge extending generally in a vertical plane and lengthwise ofthe thread to be cut, a vertically movable slide on said support member,a tracer mounted on the vertical slide and having a stylus extendinggenerally horizontally and adapted to follow the tracing edge of thetemplate, said tracer being operably connected with said cylinder tomove the support member together with the vertical slide on the carriagein said parallel direc tion and said tracing edge having a smooth,continuous contour for gradually and progressively changing the positionof the support member and the vertical slide on the carriage, whereby asthe carriage travels axially of the workpiece at said uniform rate, thecutting tool cuts a thread on the workpiece, the lead of which varies inaccordance with the relative movement between the support member and thecarriage in the direction of the carriage travel, said vertical slidehaving astraight cam edge extending in a vertical plane and inclined tothe horizontal at an angle of less than 90, said cross slide having anabutment thereon adapted to engage said cam edge such that relativehorizontal movement between the support member and the cross slideproduces sufficient vertical movement of the vertical slide to maintainthe tracer stylus in contact with said tracing edge.

2. The combination set forth in claim 1 including means for adjustingthe position of said abutment vertically on said cross slide.

3. The combination set forth in claim 1 wherein said cam edge isinclined at an angle of approximately 45 to the horizontal whereby ahorizontal movement of the tracer relative to the cross slide producesan equal vertical displacement of the tracer relative to the crossslide.

4. In a machine for cutting a thread, the lead and depth of which variesalong the axis of the thread, the combination comprising a base, meanson the base for supporting a workpiece to be threaded and for rotatingthe workpiece about a horizontal axis, a carriage on said base, meansfor moving the carriage horizontally on the base in a direction axiallyof the rotating workpiece and at a uniform rate in timed relation to thespeed of rotation of the workpiece so that the carriage moves lengthwiseof the thread to be cut at a rate corresponding to the initial lead ofthe thread to be cut, a cross slide on said carriage and movablehorizontally thereon in a direction normal to the direction of travel ofthe carriage, a first slide mounted on the cross slide and movablehorizontally thereon in a direction normal to the direction of travel ofthe carriage, a second slide mounted on said first slide and movablehorizontally thereon in a direction parallel to the path of travel ofthe carriage, a hydraulic cylinder assembly interconnecting the crossslide and the first slide for moving the first slide in said directionnormal to the path of travel of the carriage, a second hydrauliccylinder assembly interconnecting the first slide and the second slidefor moving the second slide on the first slide in said directionparallel to the path of travel of the carriage, means for mounting acutting tool on the second slide for movement therewith, a firsttemplate on said base having a tracing edge extending lengthwise of thethread to be cut and being curved in a generally horizontal plane, afirst tracer on said second slide mounted for movement therewith andhaving a vertically disposed stylus adapted to follow the tracing edgeof said first template, said first tracer being operably connected withsaid first hydraulic cylinder assembly to move said second slide in saiddirection normal to the path of travel of the carriage in response todeflection of the stylus of the first tracer, a second template on saidbase having a tracing edge which extends and is curved in a generallyvertical plane lengthwise of the thread to be cut, a vertical slide onsaid second slide, a tracer mounted on said vertical slide for movementtherewith and having a horizontally disposed stylus adapted to followthe tracing edge of the second template, said second tracer beingoperably connected with said second cylinder assembly to move saidsecond slide horizontally in said direction parallel to the path oftravel of the carriage in response to deflection of the stylus of thesecond tracer, said vertical slide having a straight cam edge thereonwhich extends in a vertical plane and is inclined to the horizontal atan angle of less than 90, said first slide having an abutment thereonadapted to engage the cam edge of the vertical slide such thathorizontal movement of the second slide relative to the first slideproduces a corresponding vertical movement of the vertical slide so asto maintain the stylus of the second tracer in contact with the tracingedge of the second template.

5. In a machine for cutting a thread, the lead of which varies along theaxis of the thread, the combination comprising a base, means on the basefor supporting a workpiece to be threaded and for rotating the workpieceabout a horizontal axis, a carriage on said base, means for moving thecarriage horizontally on the base in a direction axially of the rotatingworkpiece and at a uniform rate in timed relation to the speed ofrotation of the workpiece so that the carriage moves lengthwise of thethread to be cut at a rate corresponding to the initial lead of thethread to be cut, a cross slide on said carriage and movablehorizontally thereon in a direction normal to the direction of travel ofthe carriage, a support member mounted on the cross slide for movementhorizontally in a direction parallel to the path of movement of thecarriage, a cutting tool on said support member, a hydraulic cylinderinterconnecting the cross slide and said support member for moving thesupport member on said cross slide in said direction parallel to thepath of movement of the carriage, a template on said base having atracing edge which is curved in a vertically extending plane and whichextends lengthwise of the thread to be cut, a tracer on the supportmember mounted for movement therewith and having a tracing stylusadapted to followthe tracingedge of the template, said tracer beingoperably connected with said cylinder to move the support member on thecarriage in said parallel direction and said tracing edge having asmooth continuous contour for gradually and progressively changing theposition of the support member on the carriage whereby as the carriagetravels axially of the workpiece at said uniform rate, the cutting toolcuts a thread on the workpiece, the lead of which varies in accordancewith the relative movement between the support member and the carriagein the direction of carriage travel, a vertically shiftable slide onsaid support member on which the tracer is mounted, and means forshifting said vertical slide and the tracer thereon vertically inresponse to horizontal movement of the support member relative to thecarriage so as to maintain the tracer stylus in contact with thevertically curved tracing edge of the template.

References Cited in the file of this patent UNITED STATES PATENTS2,389,653 Turchan et al Nov. 27, 1945 2,469,262 Eggers May 3, 19492,549,024 Siepe Apr. 17, 1951 2,601,345 Turchan June 24, 1952 2,736,222Campbell Feb. 28, 1956 2,754,711 Shapiro et al. July 17, 1956 FOREIGNPATENTS 1,192,501 France Apr. 20, 1959

1. IN A MACHINE OR CUTTING A THREAD, THE LEAD OF WHICH VARIES ALONG THEAXIS OF THE THREAD, THE COMBINATION COMPRISING A BASE, MEANS ON THE BASEFOR SUPPORTING A WORKPIECE TO BE THREADED AND FOR ROTATING THE WORKPIECEABOUT A HORIZONTAL AXIS, A CARRIAGE ON SAID BASE, MEANS FOR MOVING THECARRIAGE HORIZONTALLY ON THE BASE IN A DIRECTION AXIALLY OF THE ROTATINGWORKPIECE AND AT A UNIFORM RATE IN TIMED RELATION TO THE SPEED OFROTATION OF THE WORKPIECE SO THAT THE CARRIAGE MOVES LENGTHWISE OF THETHREAD TO BE CUT AT A RATE CORRESPONDING TO THE INITIAL LEAD OF THETHREAD TO BE CUT, A CROSS SLIDE ON SAID CARRIAGE AND MOVABLEHORIZONTALLY THEREON IN A DIRECTION NORMAL TO THE DIRECTION OF TRAVEL OFTHE CARRIAGE, A SUPPORT MEMBER MOUNTED ON THE CROSS SLIDE FOR MOVEMENTHORIZONTALLY IN A DIRECTION PARALLEL TO THE PATH OF MOVEMENT OF THECARRIAGE, A CUTTING TOOL ON SAID SUPPORT MEMBER, A HYDRAULIC CYLINDERINTERCONNECTING THE CROSS SLIDE AND SAID SUPPORT MEMBER FOR MOVING THESUPPORT MEMBER ON SAID CROSS SLIDE IN SAID DIRECTION PARALLEL TO THEPATH OF MOVEMENT OF THE CARRIAGE, A TEMPLATE ON SAID BASE HAVING ATRACING EDGE EXTENDING GENERALLY IN A VERTICAL PLANE AND LENGTHWISE OFTHE THREAD TO BE CUT, A VERTICALLY MOVABLE SLIDE ON SAID SUPPORT MEMBER,A TRACER MOUNTED ON THE VERTICAL SLIDE AND HAVING A STYLUS EXTENDINGGENERALLY HORIZONTALLY AND ADAPTED TO FOLLOW THE TRACING EDGE OF THETEMPLATE, SAID TRACER BEING OPERABLY CONNECTED WITH SAID CYLINDER TOMOVE THE SUPPORT MEMBER TOGETHER WITH THE VERTICAL SLIDE ON THE CARRIAGEIN SAID PARALLEL DIRECTION AND SAID TRACING EDGE HAVING A SMOOTH,CONTINUOUS CONTOUR FOR GRADUALLY AND PROGRESSIVELY CHANGING THE POSITIONOF THE SUPPORT MEMBER AND THE VERTICAL SLIDE ON THE CARRIAGE, WHEREBY ASTHE CARRIAGE TRAVELS AXIALLY OF THE WORKPIECE AT SAID UNIFORM RATE, THECUTTING TOOL CUTS A THREAD ON THE WORKPIECE, THE LEAD OF WHICH VARIES INACCORDANCE WITH THE RELATIVE MOVEMENT BETWEEN THE SUPPORT MEMBER AND THECARRIAGE IN THE DIRECTION OF THE CARRIAGE TRAVEL, SAID VERTICAL SLIDEHAVING A STRAIGHT CAM EDGE EXTENDING IN A VERTICAL PLANE AND INCLINED TOTHE HORIZONTAL AT AN ANGLE OF LESS THAN 90*, SAID CROSS SLIDE HAVING ANABUTMENT THEREON ADAPTED TO ENGAGE SAID CAM EDGE SUCH THAT RELATIVEHORIZONTAL MOVEMENT BETWEEN THE SUPPORT MEMBER AND THE CROSS SLIDEPRODUCES SUFFICIENT VERTICAL MOVEMENT OF THE VERTICAL SLIDE TO MAINTAINTHE TRACER STYLUS IN CONTACT WITH SAID TRACING EDGE.